The present invention relates to a self-centering chuck of the type comprising false jaws slidable radially in corresponding recesses in an annular body of the chuck under the action of a rod coaxial with the chuck, jaws also slidable in the recesses and radially removable therefrom, which project from the frontal face of the chuck body and each have tangential teeth facing the corresponding false jaw, pegs movable parallel to the axis of the chuck in respective cavities in each of the false jaws and each having teeth engageable with a respective jaw, and means for moving the pegs from outside the chuck body by means of a key or similar tool, for the purpose of disengaging and re-engaging the pegs relative to the jaws.
Throughout the present description and in the claims, terms such as "radial", "axial", "longitudinal" and the like are intended to refer to the axis of the chuck, unless otherwise indicated.